Thermographic copying paper



THERMOGRAPHIC COPYING PAPER Filed May 2, 1958 lNFRA RED LAMP COUPLING COMPONENT FUSIBLE SOL-ID 16 I COLORLESS DYE BASE I Z/IRZTQS QQSEY COPYING PAPER KESlNoUs POUROUS x BlNDING AREA 3:

ORIGINAL PR I NTED AREA FAQS! H ILE COPY J9 J l L KM W ATTORNEYj United States Patent 2,967,784 THERMOGRAPHIC COPYING'PAPER Douglas A. Newman, Glen Cove, Allan T. Schlotzhauer, Locust Valley, Alfred M. Vogel, Wantagh, Donald B. Albert, Flushing, and Joseph J. Quattrone, Whitestone, N.Y., assignors to Columbia Ribbon & Carbon Manufacturing Company, Inc., Glen Cove, N.Y., a corporation of New York Filed May 2, 1958, Ser. No. 732,461

6 Claims. (Cl. 117-36) This invention relates to the art of thermography.

More particularly, it embodies the production of duplicate or facsimile copies from an original by overlaying the original with a copy sheet having on its surface a coating of thermographically sensitive materials of a novel type; then, by simply exposing the combined overlying sheets to high intensity or infrared types of irradiation, a facsimile copy of the original is produced, all without necessitating subsequent developing, fixing or similar processing of the copy sheet.

Briefly, the thus assembled original bearing an image andthe superposed copy sheet are simply fed through a machine containing a source of infrared radiation which develops the necessary heat within the imaged areas. This localized heat in the immediate vicinity of the image is transferred to the immediately adjacent copy sheet where it triggers a reaction between reagents contained on the surface of the copy sheet, thereby reproducing a copy or facsimile of the original image on the surface of the copy sheet.

Heretofore, various types of copying papers and processes utilizing such copying papers have been devised wherein facsimile copies have been produced by subjecting the copying papers to exposure of infrared light or similar forms of radiant energy in order to reproduce graphic subject matter contained on an original. Such copying papers heretofore had to be protected from light before use, or required various processing steps such as necessitating treatment with chemical solutions, drying and calendering the copy sheet before a suitable image or facsimile was reproduced.

On the contrary, the present process utilizes substantially colorless reagents generally known as Rapidogen dyes which are stabilized diazoamino dye bases or triazine types of dye bases or mixtures thereof having loosely or mechanically admixed therewith a color producing coupling agent. They are also identified herein as a complex including mixtures of triazine dye bases and diazoamino dye bases as react with a naphtol coupler to form colored compounds only when in an acid medium.

Briefly, the diazoamino dye components or bases of this invention are caused to undergo a coupling reaction with a naphtol type of coupling component and thereby form an insoluble pigment upon the establishment of an acid milieu in the immediate vicinity of the image of the original as by the melting of a solid acid material contained in the complex forming the heat-sensitive coating on the copy sheet, the melting being effected in the coating of the copy sheet by the concentration of heat from an infrared heat source producing an elevated-temperature image pattern corresponding to the graphic image irradiated and utilizing this elevated-temperature pat tern while in direct contact with the coated copy sheet to transfer the heat developed in facsimile image form to the coated copy sheet and thereby produce a corresponding visible picture or facsimile in the coated copy sheet.

The process of this invention comprises the productiqn of copies of printed pages of books or similar graphic ICC articles by the irradiation of the printed surface while in contact with a copy sheet and the resulting formation of an elevated-temperature pattern on the copy sheet and corresponding to the graphic subject matter found on the printed surface of the original, and utilizing this resultant elevated-temperature pattern concentrated in the immediately contiguous copy sheet. coated in accordance with this invention for the development of a facsimile copy of the graphic subject matter on the heat-sensitive surface of the copy sheet.

The processes of this invention embody more particularly the use of color-producing reactants, preferably two or more uncombined or mechanically juxtaposed reactants, which are present in solid particulate form with the solid particles of each reactant closely associated with the solid particles of a mutually coupling substance such as a naphtol, with all the particles nevertheless physically separated from each other by a porous binding or film-forming layer such as is readily formed by coating a transparent or translucent sup-porting base with a solution of a polyvinyl alcohol, polyvinyl butyral, methyl cellulose, Pliolite or similar synthetic rubber type of binding medium. In addition, for the purposes of carrying out the present process, a solid fusible acid is necessary, also in particulate form and dispersed throughout the film-forming layer. Such acid may be benzoic, salicylic or a similar acid fusible in the range of 60-120 C.

The reacting compositions undergo the dye forming coupling reaction when the solid acids melt and form the necessary acid milieu upon subjection of the coated copying sheet in thermographic assembly (i.e. with the copy sheet superposed over the sheet to be copied) to a melting or fusing temperature within the range of 60l20 C. by causing those overlying assembled sheets to pass under an infrared source of heat such as that provided by suitable temperature control means familiar to those versed in the art. The reacting compounds embraced herein are preferably those which in the uncombined form are uncolored or very weakly colored, but when combined give a highly desirable and sharp color reaction, a reaction which takes place practically immediately and preferably within a fraction of a second in the presence of such a melted fusible acid.

Although it is possible to have the color-producing reactants combine at room temperature in the presence of suitable solvents, it is preferred that the reagents be kept separate and dispersed from each other by the filmforming material which likewise maintains the solid fusible acid in dispersed particulate form and allows the reaction to take place only upon the fusion of the solid acid particles within the above temperature range of 60-120 C.

Manifestly, a number of processes have been heretofore devised and the prior art describes various heatsensitive paints, coated copy sheet materials and the like; however, none has been found incorporating the use of an elevated-temperature pattern to melt a solid acid material in order to produce an acid milieu wherein a coupling reaction capable of producing an insoluble pigment from a dye base and a coupling reagent in accordance with the present invention is disclosed. Such prior processes, as heretofore used], usually required extremely high temperatures, relatively long processing at these temperatures, or else the utilization of a wide range of temperatures in order to produce a readily visible change in the underlying copy sheet.

The present invention utilizes the selective absorption and conversion to heat of retained energy in the area of the printed surface in order to image the original graphic material upon the coating of the copy sheet and reproduce a visible image thereon. An area on the coating of v the copy sheet corresponding to the image on the original j exposed to the infrared radiation and immediately con- 1 tiguous to the image is thus subjected to an accumulation of heat of such intensity as to effect a melting of the solid acid contained within that area, and thus produces an acid milieu in this area which makes possible the reaction and coupling of the complex including a triazine or similar Rapidogen dye base together with its naphtol coupling component, whereupon the original pattern in facsimile is reproduced in the form of an insoluble pigment imaged on the background of the coated copy sheet.

The heat-sensitive compositions of this invention are comprised of dispersed solid reactants which are potentially chemically reactive only in an acid medium. The solid reactants thus form a complex and are physically dispersed and kept separated under normal temperature conditions; however, the melting or softening or similar physical change effected by the concentration of infrared heat passing through and concentrated within a printed image results in an immediate reaction in the contiguously assembled copy sheet and the formation of a colored opaque facsimile of the original on the copy sheet.

In carrying out the invention, light-sensitive dry copy sheets are prepared by impregnating or otherwise coating a transparent or translucent base, such as a glassine sheet, with the mixture or solution containing the dispersed heat-sensitive complex including a triazine and a naphtol coupling component together with a dispersed solid, yet readily fusible, acid reagent such as benzoic acid.

The accompanying single figure is an illustrative and not a limitative embodiment of the invention. The copying paper 11 is placed over an original sheet bearing carbon black or similar printed images thereon. The copy sheet 11 includes a foundation or carrier sheet 12 and a heat-sensitive chemically reactive layer 13 which is preferably in heat-conductive pressure contact with the printed surface of the original sheet 10. Heat radiation from lamp 20 falling on the non-printed area of sheet 10 is dissipated while that falling on original printed area 15 is absorbed and accumulated to an intensity sufiicient to melt or fuse the fusible normally solid acid particles 16 so as to produce the acid milieu necessary to enable colorless dye base particles 17 and coupling components 18 to react and produce a visible colored facsimile copy 19 which duplicates area 15. The resinous porous layer 21 serves simply to support the reactants and retain the facsimile copy 19 in position upon the cooling and resolidification of the fused material 16 and dyed facsimile image. The reproduction 19 is visible through the thin carrier sheet 12 in the form of a readily legible facsimile copy.

The following examples, of specific compositions will serve to more clearly point out and explain the novel concept herein involved.

In the present invention, the triazines, naphtols, and solid acids are dispersed and incorporated in the form of a heat-responsive complex in a coating medium as follows:

A first suspension was prepared consisting of about 0.4 gram of a triazine dye either alone or in combination with a second triazine dye of different composition such that the combination gives rise to a synergistic effect. For example, 0.39 gram of neutrazoic FFM, a triazine dye base plus a naphtol, and 0.01 gram of neutrazoic I. T., a different triazine dye plus a naphtol, were placed in a beaker. To this was added 4 grams of a vinyl chloride-vinyl acetate copolymer solution made up by mixing 10 grams of the dry granular vinyl chloridevinyl acetate copolymer known as VYHH dissolved in approximately 38 grams of toluene and about 8 grams of acetone.

A second suspension was next prepared consisting of a saturated solution of a polyamide resin in toluene by dissolving powdered polyamide resin in toluene. Thenequal parts by weight of this'polyamide resin solution and benzoic acid were mixed together, namely 2% grams of the resin solution and 2 /2 grams of powdered benzoic acid.

The final coating mixture was prepared by mixing 5 grams of the second resin suspension with approximately an equal weight of the first resin mixture. The two suspensions were then thoroughly mixed as by ball milling and the complex mixture coated on to a glassine or similar translucent paper sheet.

Many different solvents can be used; the important factor, however, is that whatever solvent is used it must not dissolve the acid specified. Examples of such solvents are toluene, acetone, xylene, and/ or other non or weakly polar solvents. Chlorinated hydrocarbons such as trichloroethylene, trichloroethane, etc. may also be used.

Any organic acid may be used which will have a melting range such that the heat developed in the copying process will be sufficient to melt the acid and thus effect a coupling reaction by bringing about the interaction of the triazine dye base and naphtol coupling agent in an acid milieu. Examples of such acids are o-toluic; 2, 5- dimethyl-benzoic; pimelic; naphthaleneacetic; p-n-amylbenzoic; 2,4-dimethoxybenzoic; p-isopropylbenzoic', picolinic; -pheny1propionic; dihydroacetic; benzene-ophosphoric; o-benzoylbenzoic; 6-diethylcarbinol; 3-cyclohexene; l-carboxylic; 2-furoic; p-tertiary-butylphenylacetie; and azelaie acids or any combination of these capable of giving a suitably convenient melting range.

Mixtures of triazine dye base and naphtol couplers are called Rapidogen type dyes. With heat alone no suitable color develops. However, upon addition of a low melting point acid (such as benzoic or salicylic acid), a color develops when the mixture is subjected to heat sufiicient to melt the solid acid.

Among the numerous so-called Rapidrogen type or simple diazine or triazine or mixed diazine and triazine dye bases which may be loosely coupled or merely mixed with a coupling agent to form an uncolored complex are the following:

Red B Color Index No. CI-l17 Blue BB AATCC Prototype No. Pr-258 Blue B Color Index No. CI-499 These dye base complexes are preferably present as the metal chloride, i.e. zinc chloride, or as the sulfonic acid salts of the diazo dye forming components.

A resin coating comprising a vinyl chloride-vinyl acetate copolymer dissolved in acetone and toluene to which the Rapidogen type dye base complex and benzoic acid ball milled in toluene is added forms a highly effective heat-responsive coating material for the copy paper.

The coupling reagents employed are of the naphtol type. Naphtols are classified in three general groups, namely the arylamides of 3-hydroxy-2-naphthoic acid, the arylamides of o-hydroxy carboxylic acids of nuclei other than naphthalene and the acylacetarylamides. As can be seen, the first two groups considered together constitute the arylamides of o-hydroxy carboxylic acids broadly, and will hereinafter be so considered as one group. A representative compound from each of the three groups respectively is given below:

Naphtol AS, also known as 3-hydroxy-2-naphthanilide AATCC Prototype No. Pr-302.

Naphtol AS-SR, also known as 2-hydroxy-2'-methylllH-benzyl-u-carbazole 3 carboxy-p-anisidide AATCC Prototype No. Pr-558.

Naphtol AS-LG, also known as a,a'-terephthaloyl-bi- 5-chloro-2,4, dimethoxyacetanilide AATCC Prototype No. Pr-505.

Various stabilizers such as sulfobenzoic acids, N- methyltaurine, sarcosine, and similar compounds may be used.

Various other binders may be used as a coating medium, namely any one of the rubber type binders, polyethylene type binders and the like.

The structure of the copy sheet material is so designed that an increase in temperature to a predetermined level allows the pigment forming reaction (i.e. coupling of the dye base with a naphtol to produce a dye pigment to take place. The reaction is believed to be initiated by the melting of the solid acid so as to form an acid milieu which triggers the coupling action. However, the invention is not to be limited by any such theory as to its actual operation. In summarizing, it seems that the application of heat results in a reaction wherein a colored, opaque, visibly different substance is produced in or on the coated copy sheet.

A rapid reaction rate is desirable particularly as in the present invention where the reactants form a. superficial coating for a copy sheet which is to be used as a heatsensitive copying paper. Such a reaction hereinabove given in more detail is readily obtained when the copy sheet in the form of a thermographic assembly (a copy sheet superposed upon a graphic subject-matter or image bearing original printed sheet) is subjected to infrared heat irradiation through a narrow range of temperatures varying between 6 or 70 C. and 120C. A range of about 20 C. and preferably less over a period of at most one second and preferably less is that most desired for effecting the fusion of the solid acid medium to produce the necessary acid milieu for triggering the coupling reaction and producing the necessary and desirable contrast and detail on the copy sheet for ready visibility of the facsmile copy of the original image.

Variations and modifications may be made within the scope of the claims and portions of the improvements may be used without others.

We claim:

1. A heat-sensitive copying paper capable of reproducing copies of heat-absorbing graphic materials by thermographic copying means upon being placed in heat-conductive relation with said copies of graphic materials and subjected to high-intensity irradiation, comprising a thin flexible backing, a heat-sensitive coating on said backing, said coating comprising a complex including a color forming solid material consisting of a colorless derivative of a dye-stuff adapted to be converted into the corresponding colored dyestutf on reaction with a coupling reagent, a coupling reagent for said color forming solid material including a compound selected from the group consisting of arylamides of o-hydroxy carboxylic acids and acytacetarylamides, and a third reagent including a solid fusible acid material inactive at temperature ranges below about 60 C., said complex being substantially uniformly distributed throughout a thin translucent plastic binder, said third reagent becoming effective at a temperature range of about 60-120" C. and forming a milieu in which the coupling reaction of the color forming solid material and the coupling reagent form a dye facsimile image of the graphic materials when heat developed in the graphic materials is transferred to the coating.

2 A heat-sensitive copying paper capable of reproducing copies of heat-absorbing graphic materials by thermographic copying means upon being placed in heat-conductive relation with said copies of graphic materials and subjected to high-intensity irradiation, comprising a thin flexible backing, a heat-sensitive coating on said backing, said coating comprising a complex including a substantially colorless dye base comprising a color forming solid material consisting of a colorless derivative of a dyestuff adapted to be converted into the corresponding colored dyestuff onireaction with a coupling reagent, a coupling reagent for said dye base including a compound selected from the group consisting of arylamides or o-hydcoxy carboxylie acids and acylacetaryla'mides, and asolid acid substantially stable in temperature ranges below about 60' C., said complex being substantially uniformly distributedthroughout a thin translucent plastic binder, said acid be coming fused and effective at a temperature range of about 60-120 C. to cause the dye base and the coupling reagent to react when heat developed in the graphic image materials is transferred to the coating to form a copy or facsimile.

3. A heat-sensitive copying paper capable of reproducing copies of heat-absorbing graphic image materials by thermographic copying means upon being placed in heat-conductive relation with said copies of the graphic image materials and subjected to high-intensity irradiation, comprising a thin flexible backing, a heat-sensitive coating on said backing, said coating comprising a com,- plex including a substantially colorless dye base comprising a color forming solidmaterial consisting of a colorless derivative of a dyestuff adapted tobe converted into the corresponding colored dyestuff on reaction with a coupling reagent, a coupling reagent for said dye base including a compound selected from the group consisting of arylamides of o-hydroxy carboxylic acids and acylacetarylamides, and a fusible acid solid in temperature ranges below about 60 C., said complex being substantially uniformly distributed throughout a thin transparent plastic binder, said binder being non-fusible at temperatures below about C., said solid acid melting to a liquid acid medium at a temperature range of about 60-120 C. to cause the dye base and the coupling reagent to react when heat developed in the graphic image materials is transferred to the coating by a heatabsorbing image. a

4. A heat-sensitive copying paper capable of reproducing copies of heat-absorbing graphic image materials by thermographic copying means upon being placed in heatconductive relation with said copies of the graphic image materials and subjected to high-intensity irradiation,.comprising a thin flexible backing, a heatsensitive coating on said backing, said coating comprising a complex ncludng partcles of a substantaliy colorless dye base comprsng a color formng sold materal consstng of a colorless derivative of a dycstuff adapted to be converted into the corresponding colored dyestuff on reaction with a.

coupling reagent, a coupling reagent for said dye base including a compound selected from the group consisting of arylamides of o-hydroxy carboxylic acids and acylacetarylamides, and a fusible acid solid in temperature ranges below about 60 C., said. complex being substantially uniformly distributed throughout a'thin transparent plastic binder, said binder being non-fusible at temperatures below about 120 C., said solid acid melting to a liquid acid medium at a temperature range of about 60-120 C. to cause the dye base and the coupling reagent to react when heat developed in the graphic image materials is transferred to the coating by a heatabsorbing image, all of said dispersed particles being stable at temperatures less than about 60 C.

5. A heat-sensitive copying paper capable of reproducing copies of heat-absorbing graphic image materials by thermographic copying means upon being placed in heatconductive relation with said copies of the graphic image materials and subjected to highintensity irradiation, comprising a thin flexible backing, a heat-sensitive coating on said backing, said coating comprising a complex including particles of a substantially colorless dye base comprising a color forming solid material consisting of a colorless derivative of a dyestulf adapted to be converted into the corresponding colored dyestuff on reaction with a coupling reagent, a coupling reagent for said dye base including a compound selected from the group consisting of arylamides of o-hydroxy carboxylic acids and acylacetarylamides, and a fusible acid solid in temperature ranges below about 60 C., said complex being substantially uniformly distributed throughout a thin transparent plastic binder, said binder being non-fusible at temperatures below about 120? C., said solid melting to a liquid acid medium at a temperature range of about 60-l20 C. to cause the dye base and the coupling reagent to react when heat developed in the graphic image materials is transferred to the coating by a heatabsorbing image, all of said dispersed particles being stable at temperatures less than about 60 C. and resulting in the formation of a visible dye when the copying paper is heated to about 120 C.

6. A heat-sensitive copying paper capable of reproducing copies of heat-absorbing graphic image materials by thermographic copying means upon being placed in heat-conductive relation with said graphic image materials and subjected to high-intensity irradiation, comprising a thin flexible backing, a heat-sensitive coating on said backing, said coating comprising a complex including a triazine dye base comprising a color forming solid material consisting of a colorless derivative of a dyestuff adapted to be converted into the corresponding colored dyestuif on reaction with a coupling reagent, a normally unreactive coupling reagent for said dye base including a compound selected from the group consisting of arylamides of o-hydroxy carboxylic acids and acylacetarylamides, and a fusible acid solid in temperature ranges below about 60 C., said complex being substantially uniformly distributed throughout a thin transparent plastic binder, said solid acid melting to a liquid acid medium at a temperature range of about 60-120 C. to cause the dye base and the coupling reagent to react when heat developed in the graphic image materials is transferred to the coating.

References Cited in the file of this patent UNITED STATES PATENTS 2,634,677 Kimkowski Apr. 14, 1953 2,813,043 Clark NOV. 12, 1957 UNITED STATES PATENT OFFICE' CERTIFICATION OF CORRECTION Patent No. 2 967 784 January 10, 1961 Douglas A, Newman et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 31,

strike out "single"; 38, for "Rapidrogen" read Rapidogen column 4, line column 5, line 7,

after "pigment" insert a closing parenthesis; line 25, for

"6" read 60 read dyestuff 7,

same column 5,

column 6, partcles of a sulostantally colorless dye base comprsng a color line 45, for "dyestuff" lines 38 to 40, for 'ncludng formng sold materal consstng of a color-" read including particles of a substantially colorless dye base comprising a color forming solid material consisting of a color same for "acidread acid Signed and sealed this 23rd day of May 1961,,

(SEAL) Attest:

ERNEST W SWIDER Attesting Officer DAVID L, LADD Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No. 26967 784 January 10 1961 Douglas A. Newman et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3 line 31 strike out "'single"; column l line 38 for "Rapidrogen" read Rapidogen column 5 line 7, after "pigment" insert a closing parenthesis; line 25 for "6" read 60 same column 5, line 4L5 for "dye stuff" read dyestuff column 6 lines 38 to 40 for "ncludhg partcles of a substantally colorless dye base comprsng a color formng -sold materal consstng of a color-=" read including particles of a substantially colorless dye base comprising a color forming solid material consisting of a color -==-g same column 6 line 75 for "acid-=-' read we acid Signed and sealed this 23rd day of May 1961,

(SEAL) V Attest:

ERNEST W, SWIDER DAVID L LADD Attesting Officer Q Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No. 2 967 784 January 10 1961 Douglas A. Newman et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3 line 31 strike out "single"; column 4 line 38, for "Rapidrogen" read Rapidogen column 5 line 7, after "pigment" insert a closing parenthesis; line 25 for "6" read 60 same column 5, line 45 for dye stuff'" read dyestuff column 6, lines 38 to 40 for "ncludng partcles of a substantally colorless dye base comprsng a color formng sold materal consstng of a color-" read including particles of a substantially colorless dye base comprising a color forming solid material consisting of a color same column 6, line 75, for "acid-' read acid Signed and sealed this 23rd day of May 1961.

(SEAL) Attest:

ERNEST We SWIDER DAVID Lo LADD Attesting Officer Commissioner of Patents 

1. A HEAT-SENSITIVE COPYING PAPER CAPABLE OF REPRODUCING COPIES OF HEAT-ABSORBING GRAPHIC MATERIALS BY THERMOGRAPHIC COPYING MEANS UPON BEING PLACED IN HEAT-CONDUCTIVE RELATION WITH SAID COPIES OF GRAPHIC MATERIALS AND SUBJECTED TO HIGH-INTENSITY IRRADIATION, COMPRISING A THIN FLEXIBLE BACKING, A HEAT-SENSITIVE COATING ON SAID BACKING, SAID COATING COMPRISING A COMPLEX INCLUDING A COLOR FORMING SOLID MATERIAL CONSISTING OF A COLORLESS DERIVATIVE OF A DYE-STUFF ADAPTED TO BE CONVERTED INTO THE CORRESPONDING COLORED DYESTUFF ON REACTION WITH A COUPLING REAGENT, A COUPLING REAGENT FOR SAID COLOR FORMING SOLID MATERIAL INCLUDING A COMPOUND SELECTED FROM THE GROUP CONSISTING OF ARYLAMIDES OF O-HYDROXY CARBOXYLIC ACIDS AND ACYLACETARYLAMIDES, AND A THIRD REAGENT INCLUDING A SOLID FUSIBLE ACID MATERIAL INACTIVE AT TEMPERATURE RANGES BELOW ABOUT 60*C., SAID COMPLEX BEING SUBSTANTIALLY UNIFORMLY DISTRIBUTED THROUGHOUT A THIN TRANSLUCENT PLASTIC BINDER, SAID THIRD REAGENT BECOMING EFFECTIVE AT A TEMPERATURE RANGE OF ABOUT 60-120*C. AND FORMING A MILIEU IN WHICH THE COUPLING REACTION OF THE COLOR FORMING SOLID MATERIAL AND THE COUPLING REAGENT FROM A DYE FACSIMILE IMAGE OF THE GRAPHIC MATERIALS WHEN HEAT DEVELOPED IN THE GRAPHIC MATERIALS IS TRANSFERRED TO THE COATING. 